Diol containing pendant antioxidant and UV absorber groups are gaining much more importance to stabilize the polyurethane and polyesters against thermal and photochemical degradation. European Patent No. 627452 A1 and 627452 B1 disclose the preparation of diols with pendant UV absorber moiety and also the preparation of polyurethane and polyesters from diols containing pendant UV absorbing group.
Most thermoplastic polymers and coating compositions are unstable to the extended exposure to heat and ultraviolet light source in atmosphere. Thermoplastics and coatings tend to demonstrate unwanted colour changes and reduced mechanical strength upon exposure to UV and thermal radiation. The preliminary effect of ultraviolet radiation on polymers is the formation of free radicals on the polymer chain, which react with atmospheric oxygen to generate peroxide groups. Furthermore, the decomposition of peroxide group leads to chain scission and formation of carbonyl groups. Irradiation in absence of oxygen causes the increase in crosslinking. Ultimately, this reflects on the mechanical properties and the colour of the polymeric materials. In order to prevent or at least retard the damage caused by these factors, stabilizers are added to the plastics.
Antioxidants are the compounds, which upon addition to the polymers are capable of preventing or retarding the reactions of degradation caused by heat and light energy in presence of oxygen. 2,6-di-tertbutyl-p-cresol is the one of the most important antioxidants, which is used commercially. There are many patents about the preparation and use of functional antioxidant in polymers and coatings viz. U.S. Pat. No. 4677154, JP5001285A2, JP6198825A2, JP6025663A2, U.S. Pat. No. 5449715, and U.S. Pat. No. 6262323.
T. Narayan and I.Grosse, U.S. Pat. No. 4677154, Jun. 30, 1987 disclose a stabilizer package for polyurethane comprising a substituted cresol and another costabilizer. This disclosure relates to elimination of discoloration in polyurethanes, particularly thermoplastic polyurethanes by the addition to the reaction mixture from 0.01 to 1 percent by weight, based on the isocyanate component, a stabilizer package characterized as BHT and a compound selected from tris(nonylphenyl) phosphite, tetrakis(2,4-di-t-butylphenyl)-4,4′-biphenylene diphosphonite, bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite, 2,2′-oxamido-bis[ethyl-3(3,5-dit-butyl-4-hydroxyphenyl)]propionate, disteryl thiodipropionate, triisodecyl phosphite, trilauryl trithiophosphite, distearyl pentaerythritol, 2,2′-ethylene bis(4,6-di-tertiarylbutylphenol), octadecyl 3-(3′,5′-di-t-butyl-4′-hydroxy phenyl)propionate, 4,4′-thio-bis(2-t-butyl-5-methylphenol), 4,4′-thio-bis(2-t-butyl-5-methylphenol), 2,2′-methylene-bis-(4-methyl-6-t-butylphenol), tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate, phenothiazine, tris(2,4-di-t-butylphenyl)phosphite, 4,4′-methylene bis(2,6-di-t-butylphenol), 2,6-di-t-butyldimethyl-aminomethylphenol and blends thereof.
Y. SUEMATSU, K. YAMAMOTO, JP5001285A2, Jan. 8, 1993 discloses the production of natural antioxidant. According to this disclosure, the process results in a natural antioxidant which gives an oxidation resistance equivalent to that given by well-known synthetic antioxidants such as BHA or BHT. Various parts of a sunflower, including flowers, leaves, stems, and roots, dried with hot air, crushed on an ultracentrifuge, and extracted with an org. common solvent such as hexane or ethyl ether. The resulting extract is concentrated under a reduced pressure, giving a natural antioxidant.
T. OKINA, K. KATO, H. SUZUKI, JP6198825A2, Jul. 19, 1994 discloses a composite structure of halogen-containing resin and polyurethane resin. The composite structure of this disclosure consists of a halogen-containing resin molded object (part) and the polyurethane resin molded object (part) coming into contact with or coming close to the halogen-containing molded object (part), 0.01-20 pts. wt. of an oxidation inhibitor is contained in the polyurethane resin compsn. at the time of the molding of the polyurethane resin molded object with respect to 100 pts. wt. of polyol contained in the polyurethane resin compsn. This oxidation inhibitor is composed of at least one of a phenolic oxidation inhibitor (BHT, BHA), a phosphorous oxidation inhibitor and a sulfur oxidation inhibitor.
A. NISHINA, S. HASHIMOTO, JP6025663A2, Feb. 1, 1994 discloses an antioxidant obtained by using torachrysone represented by a specified formula as an effective component. This antioxidant contains torachrysone of the formula as an effective component. Torachrysone (1,8-dihydroxy-2-acetyl-3-methyl-6-methoxynaphthalene) is prepared by purifying an extract from the seed of cassia tora L. or a herb such as Rheirhizoma. This antioxidant is used in an amount of 10-10000 ppm (in terms of torachrysone) based on the objective substance, e.g. food, cosmetic or medicine. It may be optionally used in combination with another additive such as tocopherol. It has an antioxidant power much stronger than that of a natural antioxidant such as tocopherol or L-ascorbic acid or a synthetic antioxidant such as BHA or BHT.
K. Plochocka et al., U.S. Pat. No. 5449715, Sep. 12, 1995 discloses a colorless, non-toxic, stabilized aqueous solution of a C1-C5 alkyl vinyl ether and maleic acid copolymers. The product comprises a colorless, stabilized aqueous solution of a C1-C5 alkyl vinyl ether and maleic acid copolymer which includes about 100 to 1,000 ppm of an additive mixture of (a) about 30-70% by weight of ethylenediaminetetraacetic acid (EDTA) or its salts, such as the disodium, trisodium, tetrasodium or disodium-calcium salts, and (b) about 30-70% by weight of a secondary additive which is an organic antioxidant and/or free radical scavenger selected from t-butylhydroquinone, propyl gallate, butylated hydroxy-anisole (BHA), butylated hydroxy-toluene (BHT), 4-hydroxymethyl-2,6-di-tert-butylphenol, 2,4,5-trihydroxy-butyrophenone (THBP) and N,N-diethylhydroxylamine, said stabilized solution exhibiting a retention of at least about 85-90% of its original viscosity after 3 months. Preferably, the solution is prepared by hydrolyzing the corresponding anhydride in the presence of said additive mixture.
Elder, Sherri et al., U.S. Pat. No. 6262323, Jul. 17, 2001 discloses polymerization inhibition of isoprene. In one preferred embodiment, the polymerization inhibiting composition includes phenylenediamine (PDA), butylated hydroxytoluene (BHT) and N,N′-diethylhydroxylamine (DEHA).
Monomeric and low molecular weight antioxidants are having limitation to their utility owing to their properties of migration and leaching. This phenomenon could lead to uneven distribution of antioxidants within the polymeric matrix. Leaching could be even more harmful as the loss of antioxidants from the polymer matrix could lead to extensive thermal and photo-degradation of the substrate. Therefore, in order to prevent the phenomena of migration and leaching, the antioxidants with polymerizing ability are being developed. This particular class of stabilizers would have even distribution within the polymer matrix and also they overcome the phenomena of migration and leaching.